obstruction call

Question
Catcher misses a pitched ball and the batter steps out of box because the runner at third is coming home...the catcher goes behind the batter and makes attempt to throw runner out at home to pitcher, who is at home plate...The catcher hits the batter in the back of the head with ball and the runner scores? what if anything should be called? is this obstruction by the batter and no score or did the batter do all they could do by stepping out of box after the missed pitch?

Answer
This is definitely a judgement call by the umpire.  The batter is obligated to get out of the way, but is not expected to have eyes in the back of their head.  Also the batter can't just go poof and disappear.  If they attempted to get out of the way, most likely no interference call.  BTW, the defense obstructs, the offense interferes.